Could you send me the memory line you used in your input file and what appears in the memory information section of your output file?
If you have 64 gb on your node, it might be a good idea to try to use only up to 80/85% of the available memory, since the operating system is using some of the available memory, therefore your choice of 3GB is -- in principle -- safe.

One way to cut on the memory usage is to add the following line just before the task mp2 line